A laser processing apparatus irradiates a laser beam, which is emitted from a laser oscillator, on an object to be processed using an optical system to perform a laser processing operation, such as marking, exposure, etching, punching, scribing, dicing, etc., on the object by the irradiated laser beam.
Recently, in order to prevent damage to a surface of the object, a method of forming a focusing point inside the object with a transmittance with respect to the laser beam and generating a crack to process the object is highlighted. For example, when a laser beam with a high output power is focused to form a focusing point inside a semiconductor wafer, a modified area is formed around the focusing point so that the crack is generated from the modified area. In addition, a laser beam is moved along a predetermined processing line of the semiconductor wafer to generate a crack row inside the object, and then the crack is extended to an external surface of the semiconductor wafer naturally or by using an external force so that the semiconductor wafer can be cut.
However, there is a disadvantage in that it is impossible to cut a semiconductor wafer with a metal layer using the laser processing method. Since the metal layer is formed to have a thickness of about 10 μm, the laser beam cannot transmit the metal layer with the thickness and thus, the crack to be necessary for the cutting cannot be formed inside the metal layer or the semiconductor wafer. Also, since the metal layer formed on a surface of the semiconductor wafer has high ductility, it is a disadvantage in that a yield is decreased during a cutting operation of the semiconductor wafer.